Presentation
1 October 2023 Suppression of Dexter transfer by covalent encapsulation for efficient matrix-free narrowband deep blue hyperfluorescent OLEDs
Hugo A. Bronstein
Author Affiliations +
Abstract
Hyperfluorescence shows great promise for the next generation of commercially feasible blue organic light-emitting diodes (OLEDs). High-gap matrices are currently the only available approach to suppress Dexter transfer to terminal emitter triplet states to approach the required levels of efficiency and stability, which unfortunately leads to overly complex device structures from a fabrication standpoint. To eliminate the need for matrices, we introduce a molecular design strategy where ultra-narrowband blue emitters are covalently encapsulated by insulating alkylene straps. OLEDs with simple emissive layers consisting of pristine thermally activated delayed fluorescence (TADF) hosts doped with encapsulated terminal emitters exhibit negligible external quantum efficiency (EQE) drops compared to non-doped devices, enabling an unprecedented maximum EQE of 21.5%. Simultaneously, ultra-narrow electroluminescence half-widths are afforded (14–15 nm) at desirable deep blue peak wavelengths (449 and 458 nm). To explain the near 100% internal quantum efficiency (IQE) in the absence of high gap matrices, we turn to transient absorption spectroscopy. Dexter transfer to terminal emitter triplets is directly observed for the first time in a hyperfluorescent system through comparison with a non-encapsulated analogue. It is unequivocally concluded that Dexter triplet transfer from a pristine TADF sensitiser host can be substantially reduced by an encapsulated terminal emitter, opening the door to highly efficient ‘matrix-free’ blue hyperfluorescence.
Conference Presentation
© (2023) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Hugo A. Bronstein "Suppression of Dexter transfer by covalent encapsulation for efficient matrix-free narrowband deep blue hyperfluorescent OLEDs", Proc. SPIE PC12659, Organic and Hybrid Light Emitting Materials and Devices XXVII, PC126590V (1 October 2023); https://doi.org/10.1117/12.2681746
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KEYWORDS
Organic light emitting diodes

Quantum emitters

External quantum efficiency

Matrices

Fabrication

Fluorescence

Internal quantum efficiency

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